Abstract:

A transfer substrate is provided with a photothermal conversion layer and
a transfer layer formed in this order on a base substrate. The transfer
layer is formed of an organic material selected from the group including
a first organic material, which has a weight decrease initiation
temperature (Tsub) of lower than 500° C. and sublimates under
atmospheric pressure, and a second organic material, which has a weight
decrease initiation temperature (Tsub) of lower than 500° C.
and satisfies the following inequality: Tsub-Tm<200°
C. (Tsub: the weight decrease initiation temperature of the second
organic material, and Tm: a melting point of the second organic
material). Also disclosed is a process for fabricating organic
electroluminescent devices by using the transfer substrate.

Claims:

1. A transfer substrate with a photothermal conversion layer and a
transfer layer formed in this order on a base substrate, whereinsaid
transfer layer is formed of an organic material selected from the group
including a first organic material, which has a weight decrease
initiation temperature Tsub of lower than 500.degree. C. and
sublimates under atmospheric pressure, and a second organic material,
which has a weight decrease initiation temperature Tsub of lower
than 500.degree. C. and satisfies the following equation
(1):Tsub-Tm<200.degree. C. (1)whereTsub: the weight
decrease initiation temperature of said second organic material,
andTm: a melting point of said second organic material.

2. The transfer substrate according to claim 1, wherein said first and
second organic materials are hole-transporting materials.

3. A process for fabricating organic electroluminescent devices by forming
a lower electrode in a pattern on a device substrate, forming on said
lower electrode an organic layer including at least a light emitting
layer, and then forming an upper electrode on said organic layer, said
process comprising the steps of:arranging a transfer substrate, which has
a photothermal conversion layer and a transfer layer formed of an organic
material in this order on a base substrate, opposite said device
substrate having said lower electrode formed thereon such that said
transfer layer is directed toward said device substrate; andirradiating
light from the outside of said base substrate to convert said light into
heat in said photothermal conversion layer such that said transfer layer
is thermally transferred onto said lower electrode to form at least said
light emitting layer of said organic layer,wherein said transfer layer is
formed of an organic material selected from the group including a first
organic material, which has a weight decrease initiation temperature
Tsub of lower than 500.degree. C. and sublimates under atmospheric
pressure, and a second organic material, which has a weight decrease
initiation temperature Tsub of lower than 500.degree. C. and
satisfies the following equation (1):Tsub-Tm<200.degree. C.
(1)whereTsub: the weight decrease initiation temperature of said
second organic material, andTm: a melting point of said second
organic material.

4. A transfer substrate with a photothermal conversion layer and a
transfer layer formed in this order on a base substrate, whereinsaid
transfer layer is formed of at least three organic material layers
stacked one over another, and two of said at least three organic material
layers located at the outer sides of said transfer layer are each formed
of an organic material selected from the group including a first organic
material, which has a weight decrease initiation temperature Tsub of
lower than 500.degree. C. and sublimates under atmospheric pressure, and
a second organic material, which has a weight decrease initiation
temperature Tsub of lower than 500.degree. C. and satisfies the
following equation (1):Tsub-Tm<200.degree. C.
(1)whereTsub: the weight decrease initiation temperature of said
second organic material, andTm: a melting point of said second
organic material.

5. The transfer substrate according to claim 4, wherein said two organic
material layers located at the outer sides of said transfer layer are
formed of the same organic material.

6. The transfer substrate according to claim 4, wherein said at least one
organic material layer held between said two organic material layers, one
being on the side of said base substrate and the other on the side of
said surface of said transfer layer, is formed of a hole-transporting
material.

7. The transfer substrate according to claim 6, wherein said two organic
material layers, one being on the side of said base substrate and the
other on the side of said surface of said transfer layer, are formed of a
hole-transporting material.

8. A process for fabricating organic electroluminescent devices by forming
a lower electrode in a pattern on a device substrate, forming on said
lower electrode an organic layer including at least a light emitting
layer, and then forming an upper electrode on said organic layer, said
process comprising the steps of:arranging a transfer substrate, which has
a photothermal conversion layer and a transfer layer formed of an organic
material in this order on a base substrate, opposite said device
substrate having said lower electrode formed thereon such that said
transfer layer is directed toward said device substrate; andirradiating
light from the outside of said base substrate to convert said light into
heat in said photothermal conversion layer such that said transfer layer
is thermally transferred onto said lower electrode to form at least said
light emitting layer of said organic layer,wherein said transfer layer is
formed of at least three organic material layers stacked one over
another, and two of said at least three organic material layers located
at the outer sides of said transfer layer are each formed of an organic
material selected from the group including a first organic material,
which has a weight decrease initiation temperature Tsub of lower
than 500.degree. C. and sublimates under atmospheric pressure, and a
second organic material, which has a weight decrease initiation
temperature Tsub of lower than 500.degree. C. and satisfies the
following equation (1):Tsub-Tm<200.degree. C.
(1)whereTsub: the weight decrease initiation temperature of said
second organic material, andTm: a melting point of said second
organic material.

Description:

CROSS REFERENCES TO RELATED APPLICATIONS

[0001]The present invention contains subject matter related to Japanese
Patent Application JP 2007-096271 filed in the Japan Patent Office on
Apr. 2, 2007, the entire contents of which being incorporated herein by
reference.

BACKGROUND OF THE INVENTION

[0002]1. Field of the Invention

[0003]This invention relates to a transfer substrate and a fabrication
process of organic electroluminescent devices, and especially to a
transfer substrate useful in the transfer of a hole-transporting material
and a process for fabricating organic electroluminescent devices by using
the transfer substrate.

[0004]2. Description of the Related Art

[0005]Organic electroluminescent devices making use of electroluminescence
of organic materials are each formed by arranging an organic layer, which
is composed of a hole transport layer and a light emitting layer stacked
together, between a lower electrode and an upper electrode, and are
attracting interests as light emitting devices enabling high-brightness
light emission by a low-voltage DC drive.

[0006]A full-color display system making use of such organic
electroluminescent devices include organic electroluminescent devices of
respective red (R), green (G) and blue (B) colors formed in arrays on a
substrate. In the manufacture of such a display system, light emitting
layers which are formed of organic light emitting materials capable of
emitting lights of the respective colors need to be formed in patterns
corresponding to the respective electroluminescence devices. The
formation of each light emitting layer in the corresponding pattern is
performed, for example, by the shadow masking process that the light
emitting material is vapor-deposited or coated through a mask formed by
providing a pattern of apertures in a sheet, or by the inkjet process.

[0007]However, the formation of a pattern by the shadow masking process
has difficulty in achieving further microfabrication and higher
integration for organic electroluminescent devices, because further
microfabrication is hardly feasible as to an aperture pattern to be
formed in a mask, and due to flexing and stretching of the mask,
difficulties are encountered in forming such patterned apertures at the
regions of electroluminescent devices with high positional accuracy. In
addition, a functional layer formed beforehand primarily of an organic
layer is prone to damage by its contact with the mask in which the
aperture pattern is formed, thereby causing a reduction in fabrication
yield.

[0008]On the other hand, the formation of a pattern by the inkjet process
can hardly realize further microfabrication and higher integration for
electroluminescent devices and an enlargement for a substrate.

[0009]As a new pattern-forming process for light emitting layers made of
organic materials and other organic layers, a transfer process making use
of an energy source (heat source), that is, the heat transfer process has
been proposed accordingly. Manufacture of a display system, which makes
use of the heat transfer process, is performed, for example, as will be
described next. Firstly, a lower electrode is formed beforehand on a
substrate for the display system (hereinafter called "the system
substrate"). On the other hand, a light emitting layer is formed
beforehand on another substrate (hereinafter called "the transfer
substrate") via a photothermal conversion layer. With the light emitting
layer and the lower electrode being positioned opposite each other, the
system substrate and the transfer substrate are arranged. A laser beam is
irradiated from the side of the transfer substrate so that the light
emitting layer is thermally transferred onto the lower electrode on the
system substrate. By causing the spot-irradiated laser beam to scan at
this time, the light emitting layer is thermally transferred onto the
lower electrode at predetermined regions with good positional accuracy
(see Japanese Patent Laid-Open Nos. 2002-110350 and Hei 11-260549).

[0010]A method is also disclosed to provide organic electroluminescent
devices with improved luminescence efficiency and brightness half-life
upon their production by the heat transfer process. According to this
method, a display substrate and a donor element are subjected to heat
treatment before thermally transferring a light emitting layer (see
Japanese Patent Laid-Open No. 2003-229259).

SUMMARY OF THE INVENTION

[0011]In the above-mentioned heat transfer process, however, the light
emitting layer, depending on the organic material employed there, is
liquefied by the irradiation with a laser beam and is hardly transferred.
In particular, a hole-transporting organic material useful in an organic
electroluminescent device remains as a part of a transfer layer in a
liquefied state on a surface of a transfer substrate because a hole
transport layer is generally formed thick. Reference is now had to FIG.
6A, which is a micrograph of a surface of a transfer substrate after
thermal transfer was performed using a transfer substrate carrying
thereon a transfer layer formed of "HT539" (trade name, product of
Idemitsu Kosan Co., Ltd.) as a hole-transporting organic material. A
plurality of liquid droplets such as that shown in a closeup photo of
FIG. 6B were confirmed to remain. As illustrated in FIG. 6C which is a
graph obtained by measuring the surface height of an X-X' cut section of
FIG. 6A, it has also been confirmed that the liquid droplets remain in a
pattern of asperities on the transfer substrate. The heat transfer
process, therefore, involves problems of a reduced luminescence
efficiency, an increased drive voltage, a reduced brightness half-life
and the like due to the failure in surely forming a hole transport layer
in a pattern.

[0012]It is desirable to provide a transfer substrate capable of surely
forming an organic material layer in a pattern on a transferred substrate
by the heat transfer process and also a process for fabricating organic
electroluminescent devices by using the transfer substrate.

[0013]In a first transfer substrate according to an embodiment of the
present invention with a photothermal conversion layer and a transfer
layer formed in this order on a base substrate, the transfer layer is
formed of an organic material selected from the group including a first
organic material, which has a weight decrease initiation temperature
(Tsub) of lower than 500° C. and sublimates under atmospheric
pressure, and a second organic material, which has a weight decrease
initiation temperature (Tsub) of lower than 500° C. and
satisfies the following equation (1):

Tsub-Tm<200° C. (1)

where [0014]Tsub: the weight decrease initiation temperature of the
second organic material, and [0015]Tm: a melting point of the second
organic material.

[0016]According to the first transfer substrate as described above, the
transfer layer vaporizes at lower than 500° C. without showing any
liquid state to assure the transfer of an organic material onto the
transferred substrate, when as the organic material, an organic material
which has a weight decrease initiation temperature (Tsub) of lower
than 500° C. and sublimates under atmospheric pressure is used.
When an organic material the weight decrease initiation temperature
(Tsub) of which is lower than 500° C. and the weight decrease
initiation temperature (Tsub) and melting point (Tm) of which
satisfy the above-described equation (1) is used, on the other hand, it
has been confirmed that as will be described in the detailed description
of the invention, the transfer of the organic material onto the
transferred substrate can be surely performed insofar as a temperature
range in which a liquid state is shown is lower than 200° C.

[0017]The present invention also provides a first process for fabricating
organic electroluminescent devices by using the first transfer substrate.
In a process for fabricating organic electroluminescent devices by
forming a lower electrode in a pattern on a device substrate, forming on
the lower electrode an organic layer including at least a light emitting
layer, and then forming an upper electrode such that the upper electrode
is stacked over the lower electrode via the organic layer, the process
includes the steps of: arranging the first transfer substrate of the
above-described construction such that the transfer layer is directed
toward the device substrate with the lower electrode formed thereon, and
irradiating light from a side of the base substrate to convert the light
into heat in the photothermal conversion layer such that the transfer
layer is thermally transferred onto the lower electrode to form at least
the light emitting layer of the organic layer.

[0018]According to the first fabrication process of organic
electroluminescent devices as described above, the use of the first
transfer substrate of the above-described construction makes it possible
to surely form at least the light emitting layer of the organic layer in
a pattern on the lower electrode by the heat transfer process.

[0019]In a second transfer substrate according to another embodiment of
the present invention with a photothermal conversion layer and a transfer
layer formed in this order on a base substrate, the transfer layer is
formed of at least three organic material layers stacked one over
another, and two of the at least three organic material layers located at
the outer sides of said transfer layer are each formed of an organic
material selected from the group including a first organic material,
which has a weight decrease initiation temperature (Tsub) of lower
than 500° C. and sublimates under atmospheric pressure, and a
second organic material, which has a weight decrease initiation
temperature (Tsub) of lower than 500° C. and satisfies the
following equation (1):

Tsub-Tm<200° C. (1)

where [0020]Tsub: the weight decrease initiation temperature of the
second organic material, and [0021]Tm: a melting point of the second
organic material.

[0022]According to the second transfer substrate as described above,
organic materials such as that described above are used in the respective
organic material layers on the sides of the base substrate and surface in
the transfer layer formed of the at least three organic material layers
stacked one over another. As will be described in the detailed
description of the invention, it has been confirmed that the transfer of
the transfer layer onto the transferred substrate can be surely performed
even when as at least one organic material layer held between the organic
material layer on the side of the base substrate and the organic material
layer on the side of the surface, an organic material of hardly
transferable properties is used.

[0023]The present invention also provides a second process for fabricating
organic electroluminescent devices by using the second transfer
substrate. In a process for fabricating organic electroluminescent
devices by forming a lower electrode in a pattern on a device substrate,
forming on the lower electrode an organic layer including at least a
light emitting layer, and then forming an upper electrode such that the
upper electrode is stacked over the lower electrode via the organic
layer, the process includes the steps of: arranging the second transfer
substrate of the above-described construction such that the transfer
layer is directed toward the device substrate with the lower electrode
formed thereon, and irradiating light from a side of the base substrate
to convert the light into heat in the photothermal conversion layer such
that the transfer layer is thermally transferred onto the lower electrode
to form at least the light emitting layer of the organic layer.

[0024]According to the second fabrication process of organic
electroluminescent devices as described above, the use of the second
transfer substrate of the above-described construction makes it possible
to surely transfer at least the light transmitting layer of the organic
layer onto the lower electrode by the heat transfer process.

[0025]As has been described above, each transfer substrate according to
the embodiments of the present invention and each fabrication process
according to the embodiments of the present invention, the fabrication
process making use of the transfer substrate, make it possible to surely
transfer at least the light emitting layer of the organic layer onto the
lower electrode by the heat transfer process, and therefore, can avoid
deteriorations in the characteristics of organic electroluminescent
devices which would otherwise occur due to incomplete transfer of the
organic layer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026]FIG. 1 is a cross-sectional view for describing a first embodiment
of the transfer substrate of the present invention;

[0027]FIG. 2 is a conceptual diagram which illustrates the states (solid,
liquid, and gas) of a certain material when the temperature (T) and
pressure (P) were varied;

[0028]FIGS. 3A through 3E are cross-sectional views of organic
electroluminescent devices in various steps of a first embodiment of the
process of the present invention for the fabrication of the organic
electroluminescent devices;

[0029]FIG. 4 is a cross-sectional view for describing a second embodiment
of the transfer substrate of the present invention;

[0030]FIG. 5 is a cross-sectional view fro describing a second embodiment
of the process of the present invention for the fabrication of organic
electroluminescent devices; and

[0031]FIG. 6A is a micrograph for describing problems of an existing
transfer substrate, FIG. 6B is a closeup photo of one of liquid droplets,
and FIG. 6C is a graph illustrating surface heights of the transfer
substrate after thermal transfer.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0032]Now the preferred embodiments of the present invention are described
in detail with reference to the accompanying drawings. In the following
description, a transfer substrate useful for the formation of a hole
transport layer of a full-color display system includes organic
electroluminescent devices of respective red (R), green (G) and blue (B)
colors formed in arrays on the substrate and a process for fabricating a
display system including a transfer process making use of the transfer
substrate are described.

First Embodiment

<Transfer Substrate>

[0033]Referring first to FIG. 1, a description will hereinafter be made of
the construction of a transfer substrate 100 according to the first
embodiment of the present invention. The transfer substrate 100 depicted
in the figure is useful, for example, for the formation of a hole
transport layer in an organic electroluminescence device, and is composed
of a photothermal conversion layer 102, an antioxidation layer 103 and a
transfer layer 104 formed in this order on a base substrate 101.

[0034]Of these, the base substrate 101 is made of a material which
transmits light hr of a predetermined wavelength to be irradiated in a
transfer to be performed using the transfer substrate 100. When a laser
beam of approx. 800 nm wavelength from a solid-state laser source is
employed as this light hr, for example, a glass substrate may be used as
the base substrate 101.

[0035]The photothermal conversion layer 102 is formed using a material,
which has a high photothermal conversion efficiency in converting the
light hr into heat and has a high melting point. When the above-mentioned
laser beam of approx. 800 nm wavelength is employed as the light hr, for
example, a metal of low reflectivity and high melting point, such as
chromium (Cr) or molybdenum (Mo), can be used preferably in the
photothermal conversion layer 102. Further, this photothermal conversion
layer 102 is supposed to be adjusted to such a thickness as enabling to
obtain a necessary and sufficient photothermal conversion efficiency.
When a Mo film is formed as the photothermal conversion layer 102, for
example, the photothermal conversion layer 102 is supposed to be used at
a thickness of 200 nm or so. This photothermal conversion layer 102 can
be formed, for example, by a sputter film-forming process. It is to be
noted that the photothermal conversion layer 102 is not limited to the
above-mentioned metal material but may be in the form of a film
containing a pigment as a light-observing material or a film made of
carbon.

[0036]On the photothermal conversion layer 102, the antioxidant layer 103
is arranged to prevent oxidation of the material that makes up the
photothermal conversion layer 102. The antioxidant layer 103 as described
above is formed with silicon nitride (SiNx), silicon oxide
(SiO2) or the like, for example, by the CVD (Chemical Vapor
Deposition) process. It is to be noted that this antioxidant layer 103
may be omitted when the photothermal conversion layer 102 is formed of an
oxidation-resistant material.

[0037]Further, the transfer layer 104 is arranged on the antioxidant layer
103. As features characteristic to the present invention, this transfer
layer 104 is formed of an organic material selected from the group
including a first organic material, which has a weight decrease
initiation temperature (Tsub) of lower than 500° C. and
sublimates under atmospheric pressure, and a second organic material,
which has a weight decrease initiation temperature (Tsub) of lower
than 500° C. and satisfies the following equation (1):

Tsub-Tm<200° C. (1)

where [0038]Tsub: the weight decrease initiation temperature of the
second organic material, and [0039]Tm: a melting point of the second
organic material.

[0040]The weight decrease initiation temperature (Tsub) indicates a
temperature at the time point that the weight of the organic material has
decreased by 5% when measured as measured under atmospheric pressure, and
therefore, serves as an index of a temperature at which the organic
material vaporizes. The melting point (Tm), on the other hand,
indicates a value measured by a differential scanning calorimeter (DSC)
under atmospheric pressure.

[0041]When an organic material, which has a weight decrease initiation
temperature (Tsub) of lower than 500° C. and sublimates under
atmospheric pressure, is used as the transfer layer 104, the transfer
layer 104 vaporizes at lower than 500° C. without showing any
liquid state so that the transfer of the organic material onto the
transferred substrate can be surely effected. As such an organic
material, "LG101C" (trade name, product of LG Chem, Ltd.) can be
mentioned, for example.

[0042]When an organic material, the weight decrease initiation temperature
(Tsub) of which is lower than 500° C. and the weight decrease
initiation temperature (Tsub) and melting point (Tm) of which
satisfy the above-described equation (1), is used as the transfer layer
104, on the other hand, it has been confirmed that as shown in the
conceptual diagram of FIG. 2, Tsub-Tm falls within a
temperature range indicative of a liquid state under atmospheric pressure
(P1) and that the transfer of the organic material onto the
transferred substrate can be surely effected when the above-mentioned
temperature range is lower than 200° C.

[0043]It is to be noted that upon formation of a hole transport layer for
each organic electroluminescent device, the hole transport layer is
formed at a thickness of 50 nm or greater in many instances and that the
use of an organic material specified as described above is important
because in the heat transfer process, the transfer becomes more difficult
as the thickness increases. It should now be assumed that this embodiment
uses a transfer substrate 100 with a transfer layer 104 formed of
α-NPD
(N,N'-bis(1-naphthyl)-N,N'-diphenyl[1,1'-biphenyl]-4,4'-diamine)
represented by the following structural formula (1), which is a
hole-transporting material, as a material satisfying the above-described
equation (1).

[0044]A description will, therefore, be made about the embodiment in which
the transfer layer 104 is formed of α-NPD. It is, however, to be
noted that, as organic materials the weight decrease initiation
temperature (Tsub) of which is lower than 500° C. and the
weight decrease initiation temperature (Tsub) and melting point
(Tm) of which satisfy the above-described equation (1), Alq3
[tris(8-hydroxyquinoline)aluminum], ADN [9,10-di(2-naphthyl)anthracene]
and CBP [4,4'-bis(9-dicarbazolyl)-2,2'-biphenyl] can be mentioned in
addition to α-NPD described above.

<Fabrication Process of Organic Electroluminescent Devices>

[0045]A description will next be made about a fabrication process of
organic electroluminescent devices, which makes use of the
above-described transfer substrate 100. As illustrated in FIG. 3A, a
system substrate 11 on which organic electroluminescent devices are to be
formed in arrays is firstly provided. This system substrate 11 is made of
a glass, silicon or plastic substrate, a TFT substrate with TFTs (thin
film transistors) formed thereon, or the like. It should now be assumed
that this system substrate 11 is made of a material having light
transparency especially when the display system to be manufactured in
this embodiment is of the transmission type that emitted light is
outputted from the side of the system substrate 11.

[0046]On the system substrate 11, a lower electrode 12 to be employed as
an anode or cathode is next formed in patterns.

[0047]It should be assumed that this lower electrode 12 is patterned in a
configuration suited for the drive system of the display system to be
fabricated in this embodiment. When the drive system of the display
system is a simple matrix system, for example, the lower electrode 12 is
formed, for example, in stripes. When the drive system of the display
system is an active matrix system that TFTs are arranged for respective
pixels, on the other hand, the lower electrode 12 is formed in patterns
corresponding to the respective pixels arranged in plural arrays such
that the lower electrode 12 is connected to the TFTs, which arranged
likewise in association with the respective pixels, via contact holes
(not shown) formed through an interlayer insulation film which covers
these TFTs.

[0048]It should also be assumed that for the lower electrode 12, a
suitable material is chosen and used depending upon the light output
system of the display system to be manufactured in this embodiment.
Described specifically, the lower electrode 12 is formed with a highly
reflective material when the display system is of the top emitting type
that emitted light is outputted from a side opposite to the system
substrate 11. On the other hand, the lower electrode is formed with a
light transmitting material when the display system is of the
transmission type that emitted light is outputted from the side of the
system substrate 11 or is of the dual-sided emission type.

[0049]For example, it is now assumed that the display system is of the top
emitting type and the lower electrode 12 is used as an anode. In this
case, the lower electrode 12 is formed with a high-reflectivity
conductive material, such as silver (Ag), aluminum (Al), chromium (Cr),
iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), tantalum (Ta), tungsten
(W), platinum (Pt) or gold (Au), or an alloy thereof.

[0050]When the display system is of the top emitting type but the lower
electrode 12 is used as a cathode, the lower electrode 12 is formed using
a conductive material having a small work function. As an example of such
a conducive material, an alloy of an active metal such as lithium (Li),
magnesium (Mg) or calcium (Ca) and a metal such as Ag, Al or indium (In),
or a material of a stacked structure of these metals can be used. It is
also possible to use, for example, a structure that a compound of an
active metal such as Li, Mg or Ca and a halogen such as fluorine or
bromine, oxygen or the like is inserted as a thin layer between the upper
electrode 12 and an organic layer to be formed above the upper electrode
12.

[0051]When the display system is of the transmission type or the
dual-sided emission type and the lower electrode 12 is used as an anode,
the lower electrode 12 is formed with a high-transmittance conductive
material such as ITO (indium-tin-oxide) or IZO (indium-zinc-oxide).

[0052]It is to be noted that, when an active matrix system is adopted as
the drive system for the display system to be manufactured in this
embodiment, the display system may desirably be designed as the top
emitting type to assure a sufficient aperture ratio for each organic
electroluminescent device.

[0053]After the lower electrode 12 (the anode in this embodiment) has been
formed as described above, an insulating film 13 is then formed in
patterns such that the insulating film 13 covers the lower electrode 12
at a periphery thereof. Portions of the lower electrode 12, which are
exposed through windows formed in the insulating film 13 as described
above, are used as pixel regions at which respective organic
electroluminescent devices are to be arranged. This insulating film 13 is
assumed to be formed, for example, by using an organic insulating
material such as a polyimide or photoresist or an inorganic insulating
material such as silicon oxide.

[0054]Subsequently, a hole injection layer 14 is formed as a layer which
commonly covers the lower electrode 12 and the insulating layer 13. This
hole injection layer 14 is formed using a general hole injection
material. For example, m-MTDATA
[4,4,4-tris(3-methylphenylphenylamino)triphenylamine] represented by the
following structural formula (2) is vapor-deposited into a film of 25 nm
in thickness.

[0055]The steps up to the immediately above step may be performed
similarly as in the manufacture of a display system making use of
ordinary organic electroluminescent devices.

[0056]As illustrated in FIG. 3B, the transfer substrate 100 is then
arranged opposite the system substrate 11 with the hole injection layer
14 formed thereon. At this time, the transfer substrate 100 and the
system substrate 11 are arranged such that the transfer layer 104 and the
hole injection layer 14 face each other. As an alternative, the system
substrate 11 and the transfer substrate 100 may be brought into close
contact with each other such that the hole injection layer 14, which
constitutes an uppermost layer on the side of the system substrate 11,
and the transfer layer 104, which constitutes an upper layer on the side
of the transfer substrate 100, come into contact with each other. Even
when arranged in this manner, the transfer layer 14 formed of the
hole-transporting material is brought into such a state as being
supported on the insulating film 13 on the side of the system substrate
11, and therefore, the transfer substrate 100 does not come into contact
with the areas of the hole injection layer 14 on the lower electrode 12.

[0057]From the side of the base substrate 101 of the transfer substrate
100 arranged opposite the system substrate 11 as described above, a laser
beam hr, for example, of 800 nm wavelength is then irradiated. At this
time, the laser beam hr is selectively irradiated in spots onto areas
corresponding to the respective pixel regions because a hole transport
layer to be described subsequently herein is common to the organic
electroluminescent devices of the respective colors.

[0058]The laser beam hr is then absorbed in the photothermal conversion
layer 102, and by using the resulting heat, the transfer layer 104 is
thermally transferred to the side of the system substrate 11. At this
time, a hole transport layer 15 is surely formed in patterns on the lower
electrode 12 through the hole injection layer 14 because the transfer
substrate 100 is provided with the transfer layer 104 made of the
hole-transporting material and constructed as described above.

[0059]In this step, it is important to perform the irradiation of the
laser beam hr such that the upper surface of the lower electrode 12, the
upper surface being exposed through the insulating film 13 at the pixel
regions, is completely covered by the hole transport layer 15.

[0060]It is desired to perform the above-mentioned heat transfer step in a
vacuum, although the heat transfer step is feasible under atmospheric
pressure. By performing the heat transfer in a vacuum, the transfer can
be effected with a laser beam hr of lower energy so that the adverse
thermal effects to be given to the hole transport layer 15 during its
transfer can be lessened. Further, the performance of the heat transfer
step in a vacuum makes it possible to enhance the close contact between
the substrates themselves and to effect the transfer with better pattern
accuracy, and therefore, is desired. Moreover, the devices can be
protected from deterioration by continuously performing all the steps in
a vacuum.

[0061]In the above-described step that the laser beam hr is selectively
irradiated in spots, it is only necessary to irradiate the laser beam hr
with an appropriate spot diameter onto the transfer substrate 100 along
the lower electrode 12 when a drive unit for a laser head in a laser
irradiation system is equipped with a precise alignment system. In this
case, it is no longer necessary to strictly perform the alignment between
the system substrate 11 and the transfer substrate 100. When the drive
unit for the laser head is not equipped with any precise alignment
system, on the other hand, it is necessary to form beforehand, on the
side of the transfer substrate, a light-shielding film that restricts
regions to be irradiated with the laser beam hr. Described specifically,
a light-shielding film formed by arranging openings in a highly
reflective metal layer which reflects a laser beam is arranged on a back
side of the transfer substrate 100. Further, a low-reflective metal may
be formed as a film on the light-shielding film. In this case, a need
arises to accurately perform the alignment between the system substrate
11 and the transfer substrate 100.

[0062]In this embodiment, the hole transport layer 15 was formed in
patterns by the single heat transfer step. When the thickness of the hole
transport layer 15 is too large to effect its transfer at once (for
example, 40 nm or greater), the hole transfer layer 15 can be formed by
performing the heat transfer step, which makes use of the transfer
substrate 100, a plurality of times.

[0063]After the above-described step, a heating step is performed.
Described specifically, the system substrate 11 is heated immediately
after the transfer of the transfer layer 104. For example, the heating
temperature may preferably be within the ±30° C. range of a
glass transition temperature (Tg) possessed by the organic material which
makes up the hole transport layer 15. When a material with no appreciable
Tg is used as the transfer layer 104, on the other hand, the range of
100° C.±50° C. is preferred as a specific heating
temperature, with the range of 100° C.±30° C. being more
preferred because the performance of the heating step in the latter range
induces no thermal degradation of the organic materials which make up the
remaining organic layers. By this heating step, the hole transport layer
15 is stabilized to achieve improvements in luminescence efficiency and
brightness half-life.

[0064]As illustrated in FIG. 3C, light-emitting layers 16 made of organic
light-emitting materials of respective colors are then formed on the hole
transport layer 15 by the vacuum deposition process. For the formation of
a blue light emitting layer 16b, a material obtained by mixing 2.5 wt %
of a styrylamine derivative, which is represented by the following
structural formula (4) and is a blue light emitting guest material, with
ADN, which is represented by the following structural formula (3) and is
an electron-transporting host material, is vapor-deposited as a film of
approx. 35 nm thickness on the hole transport layer 15 at the regions
where blue light emitting devices are to be formed.

[0065]For the formation of a red light emitting layer 16r, a material
obtained by mixing 30 wt % of
2,6-bis[(4'-methoxydiphenylamino)styryl]-1,5-dicyanonaphthalene (BSN),
which is a red light emitting guest material, with the above-described
AND as a host material, is vapor-deposited as a film of approx. 30 nm
thickness on the hole transport layer 15 at the regions where red light
emitting devices are to be formed.

[0066]For the formation of a green light emitting layer 16g, a material
obtained by mixing 5 wt % of coumarin 6, which is a green light emitting
guest material, with the above-described AND as a host material, is
vapor-deposited as a film of approx. 30 nm thickness on the hole
transport layer 15 at the regions where green light emitting devices are
to be formed.

[0067]In this embodiment, the description has been made about the example
in which the light emitting layers 16 of the respective colors were
formed in patterns by the vacuum deposition process. As in the formation
step of the hole transport layer 15, however, the light emitting layers
16 of the respective colors may be formed by the heat transfer process.

[0068]As illustrated in FIG. 3D, an electron transport layer 17 is
vapor-deposited as a common layer over the entire surface of the system
substrate 11 after the above-described step. This electron transport
layer 17 is formed with a general electron-transporting material. For
example, Alq3 is vapor-deposited at a thickness of 20 nm or so.

[0070]An electron injection layer 19 is then formed on the electron
transport layer 17 by the vacuum deposition process. This electron
injection layer 19 is vapor-deposited as a common layer over the whole
surface of the system substrate 11. This electron injection layer 19 is
formed with an ordinary electron injection material. For example, lithium
fluoride (LiF) can be formed at a film thickness of about 0.3 nm
(deposition rate: approx. 0.01 nm/sec) by the vacuum deposition process.

[0071]An upper electrode 20 is then formed on the electron injection layer
19. This upper electrode 20 is used as a cathode when the lower electrode
12 is an anode, but is used as an anode when the lower electrode 12 is a
cathode. When the display system to be manufactured in this embodiment
uses the simple matrix system, the upper electrode 20 is formed, for
example, in the form of strips which intersect with stripes of the lower
electrode 12. When the display system uses the active matrix system, on
the other hand, the upper electrode 20 is assumed to be formed in the
form of a solid film formed such that it covers the whole surface of the
system substrate 11, and to be used as an electrode common to the
respective pixels. In this case, an auxiliary electrode (not shown) may
be formed with the same material as the lower electrode 12, and the upper
electrode 20 may be connected to this auxiliary electrode to form a
construction that prevents a voltage drop at the upper electrode 20.

[0072]Red light emitting devices 21r, green light emitting devices 21g and
blue light emitting devices 21b are, therefore, formed in portions, where
the organic layers 18 including the light emitting layers 16r, 16g, 16b
of the respective colors are held, at the intersections between the lower
electrode 12 and the upper electrode 20.

[0073]For the upper electrode 20, a suitable material is supposed to be
chosen and used depending on the light output system of the display
system to be manufactured in this embodiment. Described specifically,
when the display system is of the top emitting type that emitted light is
outputted from the side opposite to the system substrate 11 or is of the
dual-sided emission type, the upper electrode 20 is formed with a light
transmitting material or semi-transmissive material. When the display
system is of the transmission type that emitted light is outputted from
the side of the system substrate 11, the upper electrode 20 is formed
with a highly reflective material.

[0074]In this embodiment, the display system is of the top emitting type
and the lower electrode 12 is used as an anode, so that the upper
electrode 20 is used as a cathode. In this case, the upper electrode 20
is formed using a material having good light transparency among the
materials having a small work function and exemplified in connection with
the formation step of the lower electrode 12 such that electrons can be
efficiently injected into the organic layer 18.

[0075]Therefore, the upper electrode 20 is formed, for example, as a
common cathode formed with MgAg at a thickness of 10 nm by the vacuum
deposition process. At this time, the formation of the upper electrode 20
is performed by a film-forming process making use of film-forming
particles of energy low enough to avoid any effect on the underlying
layers, for example, by the vapor-deposition process or the CVD (chemical
vapor deposition) process.

[0076]When the display system is of the top emitting type, it is preferred
to design such that the intensity of light to be outputted can be
increased by forming the upper electrode 20 as a semi-transmissive
electrode to construct a resonator structure between the upper electrode
20 and the lower electrode 12.

[0077]When the display system is of the transmission type and the upper
electrode 20 is used as a cathode, the upper electrode 20 is formed with
a conductive material having a small work function and a high
reflectivity. When the display system is of the transmission type and the
upper electrode 19 is used as an anode, the upper electrode 20 is formed
with a conductive material having a high reflectivity.

[0078]After the organic electroluminescent devices 21r, 21g, 21b of the
respective colors are formed as described above, a protective film 22 is
formed to cover the upper electrode 20 as illustrated in FIG. 3E. This
protective layer 22 is intended to prevent water from reaching the
organic layer 18, and is supposed to be formed at a sufficient thickness
with a material having low water permeability and water-absorbing
property. When the display system to be manufactured in this embodiment
is of the top emitting type, this protective film 22 is supposed to be
made of a material which transmits light generated in the light emitting
layers 16r, 16g, 16b of the respective colors, so that a transmittance of
80% or so can be assured, for example.

[0079]The above-described protective film 22 may be formed with an
insulating material. When the protective film 22 is formed with an
insulating material, an inorganic amorphous insulating material, for
example, amorphous silicon (α-Si), amorphous silicon carbide
(α-SiC), amorphous silicon nitride (α-Sil.sub.-xNx),
amorphous carbon (α-C) or the like can be suitably used. Such an
inorganic amorphous insulating material does not form grains and
therefore, is low in water permeability, so that the protective film 22
is provided with good waterproofing property.

[0080]When amorphous silicon nitride is used to form the protective film
22, for example, the amorphous silicon nitride is formed into a film of
from 2 to 3 μm in thickness by the CVD process. At this time, it is,
however, desired to set the film-forming temperature at room temperature
for the prevention of a reduction in brightness due to a deterioration of
the organic layer 18 and also to perform the formation of the film under
conditions that minimize the stress on the film for the prevention of
peeling of the protective layer 22.

[0081]When the display system to be manufactured in this embodiment uses
the active matrix system and the upper electrode 20 is arranged as a
common electrode covering the whole surface of the system substrate 11,
the protective film 22 may be formed with a conductive material. When the
protective film 22 is formed with such a conductive material, a
transparent conductive material such as ITO or IXO can be used.

[0082]These layers 17, 19 to 22, which cover the light emitting layers
16r, 16b, 16g of the respective colors, are each formed as a solid film
without using any mask. It is preferred to perform the formation of these
layers 17, 19 to 22 continuously in the same film-forming apparatus
desirably without exposure to the atmosphere. This makes it possible to
avoid the deterioration of the organic layer 18 which would otherwise
occur by water in the atmosphere. Further, the layers which make up the
organic layer 18 and are other than the hole transport layer 15 and light
emitting layers 16, that is, the hole injection layer 14 and electron
transport layer 17 may be formed at the pixel regions by the heat
transfer process.

[0083]To the system substrate 11 with the protective film 22 formed
thereon as described above, a protective substrate 23 is bonded on the
side of the protective film 22 via an adhesive resin material (not
shown). As the adhesive resin material, an ultraviolet-curing resin can
be used, for example. As the protective substrate 23, on the other hand,
a glass substrate can be used, for example. It is, however, to be noted
that, when the display system to be manufactured is of the top emitting
type, it is essential that the adhesive resin material and protective
substrate 23 are made of materials having light transparency,
respectively.

[0084]By the above-described steps, a full-color display system 1 with the
light-emitting devices 21r, 21g, 21b of the respective colors formed in
arrays on the system substrate 11 is completed.

[0085]According to the above-described transfer substrate 100 and the
above-described fabrication process of organic electroluminescent
devices, the fabrication process making use of the transfer substrate
100, the hole transport layer 15 can be surely formed in a pattern on the
lower electrode 12 via the hole injection layer 14 by the heat transfer
process owing to the use of the organic material, the weight decrease
initiation temperature (Tsub) of which is lower than 500° C.
and the weight decrease initiation temperature (Tsub) and melting
point (Tm) of which satisfy the equation (1). It is, therefore,
possible to avoid deteriorations of the characteristics of organic
electroluminescent devices, which would otherwise occur by incomplete
transfer of the hole transport layer 15.

[0086]In the above embodiment, the description was made primarily about
the case that the lower electrode 12 was formed as an anode and the upper
electrode 20 was formed as a cathode. The present invention can also be
applied to the case that the lower electrode 12 was formed as a cathode
and the upper electrode 20 was formed as an anode. In such a case, the
individual layers 14 to 17, 19 between the lower electrode 12 and the
upper electrode 20 are stacked in the reverse order.

[0087]The present invention described above based on the embodiment is
effective not only for devices with common layers separated as mentioned
above but also for tandem organic EL devices in each of which units of
organic layers having light emitting layers, respectively, (light
emitting units) are stacked as illustrated, for example, in Japanese
Patent Laid-Open No. 2003-272860, and can bring about similar
advantageous effects.

Second Embodiment

<Transfer Substrate>

[0088]FIG. 4 is a cross-sectional construction diagram of a transfer
substrate 100' for use in this embodiment. It is to be noted that like
elements of structure to those in the first embodiment will be described
by applying like reference numerals. As depicted in this figure, the
transfer substrate 100' is constructed by successively stacking a
photothermal conversion layer 102, an antioxidant layer 103 and a
transfer layer 104' on a base substrate 101.

[0089]In this embodiment, the transfer layer 104' is formed by stacking at
least three organic material layers one over another. Described
specifically, the transfer 104' layer is constructed by successively
stacking a first layer 104a', a second layer 104b' and a third layer
104c' from the side of the base substrate 101.

[0090]The first layer 104a' on the side of the base substrate 101 and the
third layer 104c' on the side of the surface are each formed with an
organic material selected from the group including a first organic
material, which has a weight decrease initiation temperature (Tsub)
of lower than 500° C. and sublimates under atmospheric pressure,
and a second organic material, which has a weight decrease initiation
temperature (Tsub) of lower than 500° C. and satisfies the
following equation (1):

Tsub-Tm<200° C. (1)

where [0091]Tsub: the weight decrease initiation temperature of the
second organic material, and [0092]Tm: a melting point of the second
organic material.

[0093]Therefore, the holding of second layer 104b' between the first layer
104a' and the third layer 104c', which are formed with the organic
materials satisfying the equation (1), makes it possible to surely
transfer the second layer 104b' to the side of the transferred substrate
even if the second layer 104b' is formed of a material which does not
satisfy the equation (1) and is hardly transferable. The second layer
104b' can hence be surely transferred to the side of the transferred
substrate even if the second layer 104b' is formed with a
hole-transporting material hardly transferable as a single layer and is
formed at a thickness of from 50 nm to 100 nm. The first layer 104a' and
third layer 104c' are each assumed to be formed at a thickness of from 5%
to 10% based on the total thickness of the transfer layer 104'.

[0094]When the second layer 104b' is formed with a hole-transporting
organic material, it is preferred that the first layer 104a' and third
layer 104c' are also formed with hole-transporting organic materials,
respectively. The first layer 104a' and third layer 104c' may, however,
be formed with organic materials having different properties from the
organic material of the second layer 104b, for example,
electron-transporting organic materials provided that deteriorations in
the characteristics of the resulting organic electroluminescent devices
are within permissible ranges. It is preferred, but not particularly
limited to, that the first layer 104a' and third layer 104c' are formed
with the same material, because the formation of the transfer substrate
100' is facilitated.

[0095]In the transfer substrate 100' to be employed in this embodiment,
the first layer 104a' and third layer 104c' are assumed to be formed with
"LG101C" (trade name for a hole-transporting material, product of
Idemitsu Kosan Co., Ltd.) and the second layer 104b' as a layer held
between the first layer 104a' and third layer 104c' is formed with
"HT-320" (trade name for a hole-transporting organic material, product of
Idemitsu Kosan Co., Ltd.).

[0096]It is to be noted that the above description was made about an
example in which the second layer 104b' is a single layer but the second
layer 104b' may be formed of plural layers.

<Fabrication Process of Organic Electroluminescent Devices>

[0097]The fabrication of organic electroluminescent devices, which makes
use of the above-described transfer substrate 100', is performed in a
similar manner as in the first embodiment. Described specifically, in the
step described with reference to FIG. 3B in the first embodiment, the
transfer substrate 100' is arranged opposite a system substrate 11 with a
hole injection layer 14 formed thereon, as shown in FIG. 5. At this time,
the transfer substrate 100' and the system substrate 11 are arranged such
that the transfer layer 104' and the hole injection layer 14 face each
other.

[0098]From the side of the base substrate 101 of the transfer substrate
100' arranged opposite the system substrate 11 as described above, a
laser beam hr, for example, of 800 nm wavelength is then irradiated. At
this time, the laser beam hr is selectively irradiated in spots onto
areas corresponding to the respective pixel regions because a hole
transport layer to be described subsequently herein is common to the
organic electroluminescent devices of the respective colors.

[0099]The laser beam hr is then absorbed in the photothermal conversion
layer 102, and by using the resulting heat, the transfer layer 104' is
thermally transferred to the side of the system substrate 11. As a
result, a hole transport layer 15' is surely formed in patterns on the
lower electrode 12 through the hole injection layer 14. In this case, the
hole transport layer 15' is formed of a mixture of the materials of the
respective layers of the transfer layer 104' formed of the
above-described three layers. Subsequently, the system substrate 11 with
the hole transport layer 15' formed thereon is heated at a temperature
around the Tg of the organic material which primarily makes up the hole
transport layer 15'.

[0100]In a similar manner as in the steps described with reference to
FIGS. 3C to 3E in the first embodiment, subsequent steps are conducted to
fabricate organic electroluminescent devices.

[0101]According to the above-described transfer substrate 100' and the
above-described fabrication process of organic electroluminescent
devices, the fabrication process making use of the transfer substrate
100', the hole transport layer 15' can be surely formed in a pattern on
the lower electrode 12 via the hole injection layer 14 by the heat
transfer process owing to the formation of the first layer 104a', on the
side of the base substrate, and the third layer 104c', on the side of the
surface, as the transfer layer 104' with the organic material, which has
a weight decrease initiation temperature (Tsub) of lower than
500° C. and sublimates under atmospheric temperature. It is,
therefore, possible to avoid deteriorations of the characteristics of the
organic electroluminescent devices, which would otherwise occur by
incomplete transfer of the hole transport layer 15'.

EXAMPLES

[0102]A description will next be made of fabrication procedures of organic
electroluminescent devices of specific examples of the present invention
and comparative examples to these specific examples and also of their
evaluation results.

Examples 1 to 5

[0103]In a similar manner as the procedure described above with reference
to FIG. 1 in the first embodiment, transfer substrates 100 were
fabricated by varying the material of the transfer substrate 104. As will
be shown below in Table 1, a transfer layer 104 was formed, as Example 1,
with "LG101C" (trade name, product of LG Chem, Ltd.) which has a weight
decrease initiation temperature (Tsub) of lower than 500° C.
and sublimates under atmospheric temperature. As Examples 2 to 5,
transfer layers 104 were formed with organic materials, the weight
decrease initiation temperature (Tsub) of each of which is lower
than 500° C. and the weight decrease initiation temperature
(Tsub) and melting point (Tm) of each of which satisfy the
above-described equation (1). Specifically, the transfer layers 104 were
formed with Alq3 in Example 2, ADN in Example 3, α-NPD in
Example 4, and CBP in Example 5.

[0104]As Comparative Examples 1 and 2 to the above-described Examples 1 to
5, there were also prepared transfer substrates having transfer layers
104 formed with organic materials which as shown above in Table 1, are
not sublimable materials and do not satisfy the equation (1).
Specifically, the transfer layers 104 were formed with "HT-320" (trade
name, product of Idemitsu Kosan Co., Ltd.) in Comparative Example 1 and
"HT-539" (trade name, product of Idemitsu Kosan Co., Ltd.) in Comparative
Example 2.

[Evaluation Results]

[0105]Using the above-mentioned transfer substrates of Examples 1 to 5 and
those of Comparative Examples 1 and 2, patterns were formed on
transferred substrates by the heat transfer process. The results are
shown above in Table 1. In Table 1, "SUCCEEDED" indicates that the
pattern formation was surely effected, while "FAILED" indicates that the
transfer was not effected and the transfer layer remained as liquid
droplets on the transfer substrate. As shown in Table 1, the sure pattern
formation onto the transferred substrate was confirmed (SUCCEEDED) when
the transfer substrate 100 of each of Examples 1 to 5 was used. On the
other hand, no transfer was confirmed to take place (FAILED) in
Comparative Examples 1 and 2 in which the values of Tsub-Tm
were greater than 200° C.

Examples 6 to 10

<Transfer Substrates>

Example 6

[0106]A transfer substrate 100' was prepared as will be described next.
Firstly, a photothermal conversion layer 102 made of Mo and having a
thickness of 200 nm was formed on a base substrate made of a glass
substrate by the general sputtering process. On the photothermal
conversion layer 102, an antioxidation layer 103 made of SiNx was
then formed at a thickness of 100 nm by the CVD process.

[0107]Subsequently, a first layer 104a', second layer 104b' and third
layer 104c' were successively formed with the organic materials and
thicknesses shown in Table 2, respectively, so that a transfer layer 104'
was formed.

[0108]In this embodiment, "LG101C" (trade name, product of LG Chem, Ltd.)
which has a weight decrease initiation temperature (Tsub) of lower
than 500° C. and sublimates under atmospheric pressure was used
for the first layer 104a' and third layer 104c', and "HT-320" (trade
name, product of Idemitsu Kosan Co., Ltd.) which is a hole-transporting
material hardly transferable as a single layer was employed for the
second layer 104b'.

Example 7

[0109]In this embodiment, a transfer substrate 100' was prepared in a
similar manner as in Example 6 except that α-NPD, a
hole-transporting material the weight decrease initiation temperature
(Tsub) of which is lower than 500° C. and the weight decrease
initiation temperature (Tsub) and melting point (Tm) of which
satisfy the above-described equation (1), was used for the first layer
104a' and third layer 104c'.

Example 8

[0110]In this embodiment, a transfer substrate 100' was prepared in a
similar manner as in Example 6 except that the above-described "LG101C,"
a hole-transporting material, was used for the first layer 104a' and
Alq3, an electron-transporting material the weight decrease
initiation temperature (Tsub) of which is lower than 500° C.
and the weight decrease initiation temperature (Tsub) and melting
point (Tm) of which satisfy the above-described equation (1), was
employed for the third layer 104c'.

Example 9

[0111]In this embodiment, a transfer substrate 100' was prepared in a
similar manner as in Example 6 except that the above-described
α-NPD was used for the first layer 104a' and the above-described
Alq3 was employed for the third layer 104c'.

Example 10

[0112]In this embodiment, a transfer substrate 100' was prepared in a
similar manner as in Example 6 except that Alq3, an
electron-transporting material the weight decrease initiation temperature
(Tsub) of which is lower than 500° C. and the weight decrease
initiation temperature (Tsub) and melting point (Tm) of which
satisfy the above-described equation (1), was used for the first layer
104a' and third layer 104c'.

Comparative Examples 3 to 5

[0113]As Comparative Example 3 to Examples 6 to 10, a transfer substrate
was prepared in a similar manner as in Example 7 except that the transfer
layer 104' was formed with only "HT-320" (trade name, product of Idemitsu
Kosan Co., Ltd.). As Comparative Example 4, a transfer substrate was
prepared in a similar manner as in Example 7 except that a third layer
made of the above-described Alq3 alone was formed only on the side
of a surface of "HT-320" (as a second layer). Further, as Comparative
Example 5, a transfer substrate was prepared in a similar manner as in
Example 7 except that a first layer made of α-NPD was formed only
on the side of a base substrate of "HT-320" (as a second layer).

<Fabrication Process of Organic Electroluminescent Devices>

[0114]Using the above-mentioned transfer substrates 100' of Examples 6 to
10 and the above-mentioned transfer substrates of Comparative Examples 3
to 5, organic electroluminescent devices, that is, blue-light emitting
devices were formed in a similar manner as in the second embodiment,
respectively.

[0115]Prepared firstly were cells for top-emitting organic
electroluminescent devices, which on a system substrate 11 made of a
glass plate of 30 mm×30 mm, carried as a lower electrode (anode) 12
an ITO transparent electrode of 12.5 nm in thickness stacked on a Ag
alloy (reflective layer) of 190 nm in thickness. An insulating film 13 of
silicon oxide was then formed at a thickness of about 2 μm by the
sputtering process to cover the lower electrode 12 at a periphery
thereof, and by a lithographic process, the lower electrode 12 was
exposed as pixel regions.

[0116]As a hole injection layer 14 in the form of an organic layer, a film
made of m-MTDATA was then formed at a thickness of 12 nm (deposition
rate: 0.2 to 0.4 nm/sec) by the vacuum deposition process.

[0117]The transfer substrate 100' of Example 6, on which a transfer layer
104' of the above-mentioned construction had been formed, was arranged
opposite the system substrate 11 with the hole injection layer 14 formed
thereon, and in a vacuum, those transfer substrate and system substrate
were brought into close contact with each other. A small clearance of
about 2 μm was retained between those substrates because of the
thickness of the insulating film 13. In this state, a laser beam hr of
800 nm wavelength was irradiated corresponding to the pixel regions of
the device-fabricating system substrate 11 from the side of the base
substrate 101 in the transfer substrate 100'. As a result, the transfer
layer 104' was thermally transferred from the transfer substrate 100' to
form a hole transport layer 15. The spot size of the laser beam hr was
controlled at 300 μm×10 μm. The laser beam hr was caused to
scan in a direction perpendicular to the lengthwise dimension of the
beam. The energy density was controlled at 2.6 E-3 mJ/μm2.

[0118]Subsequently, the system substrate 11 with the hole transport layer
15 formed thereon was subjected to a heating step at 100° C. for
30 minutes under an atmosphere of nitrogen as an inert gas.

[0119]A blue-light emitting layer 16b made of ADN as a host material and a
styrylamine derivative mixed as a blue-light emitting guest material at a
relative thickness ratio of 2.5% was then formed at 35 nm by vacuum
evaporation.

[0120]Subsequent to the formation of the blue-light emitting layer 16b, an
electron transport layer 17 was formed. As the electron transport layer
17, Alq3 was vapor-deposited at a thickness of 20 nm or so. As an
electron injection layer 18, LiF was then vapor-deposited at a thickness
of about 0.3 nm (deposition rate: approx. 0.01 nm/sec). As a cathode to
be employed as the upper electrode 20, MgAg was then vapor-deposited at a
thickness of 10 nm to obtain blue-light emitting devices. Organic
electroluminescent devices of Examples 7 to 10 and Comparative Examples 3
to 5 were fabricated in a similar manner as in Example 6.

[Evaluation Results]

[0121]Table 2 shows voltages and current efficiencies at 10 mA/cm2 of
the blue-light emitting devices fabricated with the transfer substrates
of Examples 6 to 10 and Comparative Examples 3 to 5 by the
above-mentioned fabrication process. As shown in Table 2, it was
confirmed that the transfer was surely effected in the organic
electroluminescent devices fabricated with the transfer substrates 100'
of Examples 6 to 10 of the construction that the second layer 104b' made
of "HT-320" was held between the first layer 104a' and third layer 104c'
each of which was made of the organic material which has a weight
decrease initiation temperature (Tsub) of lower than 500° C.
and sublimates under atmospheric pressure or an organic material the
weight decrease initiation temperature (Tsub) of which is lower than
500° C. and the weight decrease initiation temperature (Tsub)
and melting point (Tm) of which satisfy the above-described equation
(1).

[0122]In Comparative Examples 3 and 4, on the other hand, the hole
transport layer 15 was not formed in a pattern. In Comparative Example 6
in which only the first layer 104a' was formed with α-NPD, the hole
transport layer 15 was formed in a pattern but the pattern configuration
was incomplete. It was, therefore, confirmed that the drive voltage was
high and the current efficiency was low.

[0123]Among the transfer substrates of Examples 6 to 10, the transfer
substrates of Examples 6 and 7, in each which the first layer 104a' and
the third layer 104c' were both made of the same hole-transporting
material, were lower in drive voltage and higher in current efficiency
than the transfer substrates of Examples 8 to 10 in each of which at
least one of the first layer 104a' and third layer 104c' is made of the
electron-transporting material.

[0124]It should be understood by those skilled in the art that various
modifications, combinations, sub-combinations and alterations may occur
depending on design requirements and other factor in so far as they are
within the scope of the appended claims or the equivalents thereof.